Connected: An Internet Encyclopedia
RFC 1042 - Interoperation with Ethernet

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### Interoperation with Ethernet

It is possible to use the Ethernet link level protocol [12] on the same physical cable with the IEEE 802.3 link level protocol. A computer interfaced to a physical cable used in this way could potentially read both Ethernet and 802.3 packets from the network. If a computer does read both types of packets, it must keep track of which link protocol was used with each other computer on the network and use the proper link protocol when sending packets.

One should note that in such an environment, link level broadcast packets will not reach all the computers attached to the network, but only those using the link level protocol used for the broadcast.

Since it must be assumed that most computers will read and send using only one type of link protocol, it is recommended that if such an environment (a network with both link protocols) is necessary, an IP gateway be used as if there were two distinct networks.

Note that the MTU for the Ethernet allows a 1500 octet IP datagram, with the MTU for the 802.3 network allows only a 1492 octet IP datagram.

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Connected: An Internet Encyclopedia
RFC 1042 - Interoperation with Ethernet